1. Technical Field of the Invention
The present invention relates to potentiometers designed to provide voltage selection over a continuous range of voltages. More particularly, the present invention relates to a touch-controlled circuit apparatus which provides voltage selection over a first continuous range of voltages while providing either separately or simultaneously for voltage selection over additional discrete and/or continuous ranges of voltages.
2. The Prior Art
Potentiometers for controlling voltage selection are used in numerous types of applications in both home and industry. For example, these devices may be used in the control panels of such things as aircraft and aerospace applications, large construction equipment, computers, lighting systems, arcade games, or kitchen appliances, to name just a few.
In the past the prior art potentiometers for providing voltage selection having typically been of three types. One type provides a manually operated mechanical wiper that is typically controlled by a knob or slider on a control panel. The wiper is always on contact with a resistive element, which provides for voltage selection over a continuous range of voltages. The constant mechanical contact between the wiper and resistive element tends to accelerate the wear and eventual destruction of this type of potentiometer.
A second, more recent type of potentiometer provides an elongated resistive element and an elongated wiper that is parallel to and spaced from the resistive element. See, for example, U.S. Pat. Nos. 3,624,584 (Ahno) and 3,699,492 (Yoshihara). In this type of potentiometer, the elongated wiper is not in constant contact with the resistive element, but achieves voltage selection by depressing the wiper at selected locations along its length to bring it into contact with the resistive element, which has a voltage applied to it. Although this type of device reduces wear, it is not possible to produce a continuous range of output voltage levels because the wiper in this type of prior art device is typically segmented. Thus, there is some sacrifice in the ability to accurately control voltage selection, which makes the device less versatile.
Recently, there has been devised yet another type of potentiometer. See, for example, U.S. Pat. Nos. 3,895,288 and 3,968,467 (both to Lampen, et al.). This type of device typically includes a continuous length of electrically resistive material, a corresponding continuous length of electrically conductive material which serves as the wiper, and an electrically insulating spacer which serves to simultaneously support and separate the resistive and conductive materials. Either one or both of the resistive and conductive materials are designed as flexible members so that they can be pressed together at any selected location along their length to bring them into electrical contact with each other.
If a voltage is applied across the resistive material, a voltage gradient is established along the length of the material. The voltage gradient may be a linear or non-linear function of the material's length depending upon the particular composition of resistive materials used. Thus, touching either the top or bottom surface of the flexible member will cause the resistive and conductive materials to contact each other, producing a voltage output on the conductive material or wiper. The advantage of this device is that it minimizes wiper contact and reduces wear and yet provides a continuous range of output voltage levels, since the conductive wiper is not segmented.
There are many applications where it is desirable to combine both potentiometers (which provides voltage selection over a continuous range of voltages) and devices such as switches which permit selection of discrete voltages. For example, in nearly every application involving voltage selection over continuous ranges of voltages, there is also a need for at least an on/off switch.
In addition, in many applications involving computers, motor controls, level controls and the like, switches and potentiometers are required to work in tandem simultaneously for selecting such things as cursor position, motor speed and direction. Thus, in prior art applications, several separate types of voltage selection devices have been required in most electrical control panels. As a result of this problem, there have been some attempts to combine the continuous range and discrete voltage selection components in a single element. Such attempts are reflected in U.S. Pat. Nos. 3,626,350 (Suzuki) and 3,624,583 (Nakada).
In the Suzuki patent, plural potentiometers are oriented in side-by-side parallel relationship, and in the Nakada patent, there are a series of switches aligned with one another in parallel relationship to a linear potentiometer. In the case of parallel potentiometers, Suzuki expressly prevents simultaneous actuation of two or pore potentiometers when touch pressure is applied to only one. Thus, Suzuki is not useable in applications where simultaneous control of plural potentiometers is desirable. Further, the cost of both the Suzuki and Nakada devices is increased by virtue of the need for isolating structure between the parallel components.
It would reduce the cost and overall dimensions of a device having both potentiometers and discrete voltage switches if the potentiometer and switches could be constructed so as to utilize the same longitudinal conductive element for transmitting the selected voltages. However, this improvement has not been possible in the prior art because prior art devices require that the individual potentiometers extend over the entire useful length of the element.
It should also be noted that, in some applications, it is desirable to actuate two potentiometers, two switches, or a potentiometer and a switch simultaneously, with the option available for sequential operation controlled by the level of applied pressure. This situation would exist, for example, where a single controller is used to operate several processes or machines in performing simultaneous and identical functions. The prior art devices do not provide for this feature.
For some applications, it is desirable to provide a sample and hold output circuit which is actuated when the touch controlled component is actuated to store the voltage applied to the electrically conductive surface. A prior art sample and hold circuit of this type is disclosed in the aforementioned Lampen et al. patent (U.S. Pat. No. 3,968,497). This patent discloses a voltage comparator which actuates a switch to charge a capacitor across a pair of resistors and through a diode whenever the touch-controlled element is actuated. It is believed that these circuit components are not all required in order to accomplish the intended function of sampling and storing the output signal from the control device.
The pressure activated control devices of the prior art are generally fabricated from two separate layers of material, each bearing the required electrical characteristics in their surfaces. Spacer means are then disposed between the layers to maintain separation of the surfaces in the absence of actuation pressure. The process of separately forming and bonding these individual layers and spacer members in order to assemble the final element is relatively time-consuming and expensive.
In light of the above, it would be a great improvement in the art to provide a pressure activated control circuit apparatus for providing voltage selection over a first continuous range of voltages which also providing, either separately or simultaneously, for voltage selection over additional discrete and/or continuous ranges of voltages. It would be a further important improvement to provide such an apparatus which utilizes a small number of component parts, which is compact in configuration, and which is simple and inexpensive to manufacture.